The present invention relates to a subscriber telephone station connected in a dial network composed of a plurality of subscribers.
German Auslegeschrift [published patent applicational] No. 1,566,826 discloses a paging device in a branch exchange telephone system wherein, when a subscriber of the branch exchange places a call, there is actuated at the number of the called subscriber in the branch exchange, in addition to the normal call signal, a special search signal coming from a search device, whereupon the branch exchange telephone system is connected with the call transmitter of a paging system operating with wireless transmission by means of a signal converter which constitutes the search device and causes the transmission by the call transmitter of an identifying sound sequence which corresponds to the dialed number.
With this paging device it is possible to reach a subscriber either through his branch exchange terminal or through his portable transmitting/receiving device, the identifying sound sequence being transmitted only subsequent to a plurality of call signals for the called branch exchange subscriber, and a voice connection is established by the called person by means of a return signal transmitter. The voice connection is established with the calling branch exchange subscriber by a wireless link between the called person and the central exchange of the paging device and by a wire link between this central exchange and the branch exchange and the calling subscriber.
The drawback in this paging device is that only one conversation can take place at any one time if only one single carrier frequency is available for the device.
Conventional telephone instruments are composed of a handset containing a microphone and loudspeaker capsule. They have the drawback that during a telephone call it is impossible, or possible only with difficulty, to simultaneously perform manual operations because one hand is occupied. There are of course speaker telephones which, however, can be used only in small or medium size rooms. If, when a call is coming in, the subscriber is outside this room he must, if he hears the ring at all, go to the telephone instrument in order to actuate it to receive the call.